Figure 4. Amplitude histograms for detected C_m steps in unstimulated and high [Ca²⁺]_i stimulated cells.

A(i) and B(i), the amplitude histograms for all exocytotic (positive) and endocytotic (negative) events detected during 1900 s of recording from four unstimulated cells (mean p-p noise 1.56 ± 0.39 fF; A), and 1920 s of recording during periods of stimulation by high [Ca²⁺]_i in eight cells (mean p-p noise 1.56 ± 0.40 fF; B). The inset in each case shows the exocytotic events amplitude histogram on an expanded Y scale. A(ii) and B(ii), the same data on expanded X and Y scales, respectively, with the calculated distribution of WPb C_m superimposed on both the exocytotic and endocytotic distributions. The difference histogram (stimulated - unstimulated), displayed in the same way, is shown in C(i) and C(ii). The vertical lines on the lower panels indicate the region of the detected C_m steps used to calculate the frequency and kinetics of WPb exocytosis.